My intention with this blog is to share some of the more interesting curiosities of math. Often in the form of mathematical puzzles, riddles or paradoxes. Some can be applied to the real world, showing that all is not always what it seems. I'll include a calculation now and then but will keep it light — heck I'm far from a math wizz myself.

Friday, October 24, 2014

Given the following four numbers:1 5 6 7
The goal is to make the number:21
Using only these elementary arithmetic operations:( + − × ÷ )

So, you can put the four numbers in any order, and use parentheses to specify operator precedence. Each number may only be used once and must be used separately (i.e. no sticking numbers together). You do not necessarily need to use all the operators.